This invention relates generally to machining gas turbine engines and, more particularly, to an apparatus for machining turbine component internals.
A gas turbine engine includes turbine components coupled in serial flow arrangement about a rotational centerline axis. The turbine components include a fan assembly which compresses airflow entering the engine, a high pressure compressor, a combustor which burns a mixture of fuel and air, and a turbine which includes a plurality of blade assemblies that extract rotational energy from airflow exiting the combustor. The turbine engine includes both a high pressure turbine and a low pressure turbine. The high pressure turbine drives the high pressure compressor and the low pressure turbine drives the fan assembly about the centerline axis. Each of the high pressure turbine, the high pressure compressor, the low pressure turbine, and the fan assembly includes a central bore extending therethrough about the rotational centerline axis.
During turbine manufacture, weld material known as weld flash may be formed adjacent to welds on a surface defining the central bore. Such material is machined to facilitate preventing damage to the weld or the turbine component. Furthermore, machining weld flash facilitates turbine balance and high speed turbine operation. For example, the fan assembly includes a fan casing enclosing blades mounted to a fan disk. The fan disk includes an inner surface and an outer surface. The blades extend radially outward from the outer surface, while the hubs extend radially inward from the inner surface on web structures. Between hubs is a spacer section that includes an inner wall. At least some known fan disks include spacer sections welded together at a spacer weld. During fan disk manufacture, weld flash forms adjacent to the spacer weld on the spacer inner wall. A cutting tool assembly is used in conjunction with a lathe to machine weld flash adjacent to the spacer weld on the spacer inner wall. However, machining the spacer weld flash may be a challenge because at the fan hubs the fan assembly may be large and the bore may restrict access, such that a large radial distance is created between a fan assembly central bore and the spacer inner wall.
To facilitate removing weld flash in these areas some known cutting tool assemblies include extendable blades. Because of a complexity of such cutting tool assemblies removing such weld flash may be time-consuming and costly.
In one aspect, a method is provided of machining a turbine component using a cutting tool assembly and a lathe. The turbine component including a centerline axis, a central bore, an inner wall, at least one weld, and weld flash that is adjacent a weld on the inner wall. The method includes providing a cutting tool assembly which includes a centerline axis, a substantially solid toolblock body, a lead screw, a blade sub-assembly, and a cutting insert. The method further includes positioning the toolblock body in the lathe, positioning the cutting tool assembly within the turbine component central bore, and extending the blade sub-assembly to be adjacent the turbine component inner wall. The method also includes positioning the cutting tool assembly about the cutting tool assembly axis and moving the cutting tool assembly centerline axis about the rotating turbine component centerline axis such that the weld flash is removed using the cutting insert.
In another aspect, a cutting tool assembly for machining a turbine component includes a substantially solid toolblock body, a blade sub-assembly, a cutting insert, and a lead screw. The toolblock body includes a centerline axis. The blade sub-assembly is slidably retained adjacent said toolblock body and a cutting insert is attached to the blade sub-assembly. The lead screw coupled adjacent to the toolblock body such that the lead screw is substantially perpendicular to the centerline axis. The lead screw is rotatably coupled to the blade sub-assembly such that rotation of the lead screw extends the blade sub-assembly from the toolblock body.
In a further aspect, a machining assembly is provided that includes a turning lathe and a cutting tool assembly coupled to the turning lathe. The cutting tool assembly includes a substantially solid toolblock body including a centerline axis, a blade sub-assembly slidably retained adjacent the toolblock body, a cutting insert attached to the blade sub-assembly, and a lead screw adjacent the toolblock body. The lead screw is substantially perpendicular to the centerline axis and is rotatably coupled to the blade sub-assembly such that rotation of the lead screw extends the blade sub-assembly from the toolblock body.